Radio-frequency module

ABSTRACT

A semiconductor device including a radio-frequency amplifier circuit and a band selection switch is mounted on or in a module substrate. An output matching circuit coupled between the radio-frequency amplifier circuit and the band selection switch is on or in the module substrate. The semiconductor device includes a first member at which the band selection switch having a semiconductor element made of an elemental semiconductor is formed and a second member joined to the first member in surface contact therewith. The radio-frequency amplifier circuit including a semiconductor element made of a compound semiconductor is formed at the second member. Conductive protrusions are raised from first and second members. The semiconductor device is mounted on or in the module substrate with the conductive protrusions interposed therebetween, and in plan view, is in close proximity to the output matching circuit or overlaps a passive element constituting the output matching circuit.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefit of priority to Japanese PatentApplication No. 2020-205984, filed Dec. 11, 2020, the entire content ofwhich is incorporated herein by reference.

BACKGROUND Technical Field

The present disclosure relates to a radio-frequency module.

Background Art

Radio-frequency (RF) front-end modules capable of both transmitting andreceiving radio-frequency signals are installed in electronic devicesfor communications such as mobile communications and satellitecommunications. An RF front-end module includes, for example, amonolithic microwave integrated circuit (MMIC) capable of amplifyingradio-frequency signals, a control integrated circuit (IC) forcontrolling a radio-frequency amplifier circuit, a switch IC, and aduplexer.

U.S. Patent Application Publication No. 2015/0303971 discloses aradio-frequency module miniaturized by stacking a control IC on an MMIC.The radio-frequency module disclosed in U.S. Patent ApplicationPublication No. 2015/0303971 includes the MMIC mounted on a modulesubstrate and the control IC stacked on the MMIC. Electrodes of theMMIC, electrodes of the control IC, and electrodes on the modulesubstrate are electrically coupled to each other by wire bonding.

SUMMARY

In a radio-frequency amplifier circuit, for example, a heterojunctionbipolar transistor (HBT) is utilized. While an HBT operates, the HBTgenerates heat because collector dissipation occurs. A temperature riseof the HBT caused by heat generation in turn increases collectorcurrent. When conditions for this positive feedback are satisfied,thermal runaway occurs in the HBT. To avoid thermal runaway in the HBT,an upper limit of output power of the HBT is set.

To implement radio-frequency amplifier circuits with high power output,it is desirable to improve the characteristic of heat released from asemiconductor device including, for example, an HBT. It is difficult tosatisfy recent demand for radio-frequency amplifier circuits with highpower output by using the radio-frequency module disclosed in U.S.Patent Application Publication No. 2015/0303971. Additionally, when theoperating frequency is relatively high, loss in signal transfer tends toincrease. Accordingly, the present disclosure provides a radio-frequencymodule capable of suppressing increases in signal transfer loss and alsoimproving the characteristic of heat released from a semiconductordevice.

An aspect of the present disclosure provides a radio-frequency moduleincluding a module substrate, a semiconductor device mounted on or inthe module substrate and including a radio-frequency amplifier circuitand a band selection switch, and an output matching circuit disposed onor in the module substrate and coupled between the radio-frequencyamplifier circuit and the band selection switch. The band selectionswitch is configured to output from a contact selected from a pluralityof contacts an inputted radio-frequency signal. The semiconductor devicefurther includes a first member including the band selection switchincluding a semiconductor element made of an elemental semiconductor, asecond member joined to the first member in surface contact with thefirst member, the second member including the radio-frequency amplifiercircuit including a semiconductor element made of a compoundsemiconductor, and a plurality of conductive protrusions arranged atpositions included in the first member or the second member in planview. The semiconductor device is mounted on or in the module substratewith the plurality of conductive protrusions interposed between thesemiconductor device and the module substrate such that the secondmember faces the module substrate. The semiconductor device is disposedin close proximity to the output matching circuit in plan view, or thesemiconductor device overlaps at least one passive element constitutingthe output matching circuit in plan view.

The second member including the radio-frequency amplifier circuit isjoined to the first member including the band selection switch, andconsequently, the radio-frequency module can be smaller than if theradio-frequency amplifier circuit and the band selection switch areindividually mounted on or in the module substrate. Two heat transferpaths are formed; one is a heat transfer path from the semiconductorelement included in the radio-frequency amplifier circuit to the firstmember; and the other is a heat transfer path from the semiconductorelement to the module substrate via the conductive protrusion. As aresult, it is possible to improve the characteristic of heat releasedfrom the semiconductor element included in the radio-frequency amplifiercircuit.

No circuit component except the components constituting the outputmatching circuit is disposed between the passive element included in theoutput matching circuit and the semiconductor device in plan view, orthe passive element constituting the output matching circuit overlapsthe semiconductor device in plan view. As a result, it is possible toclose the distance between the semiconductor device and the outputmatching circuit. Consequently, it is possible to close the distancefrom each of the radio-frequency amplifier circuit and the bandselection switch that are disposed in the semiconductor device to theoutput matching circuit. Because this shortens the transfer line fromthe radio-frequency amplifier circuit to the output matching circuit andthe transfer line from the output matching circuit to the band selectionswitch, it is possible to reduce transfer loss.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an arrangement of constituent elements of aradio-frequency module according to a first embodiment in plan view;

FIG. 1B schematically illustrates a sectional structure of theradio-frequency module;

FIG. 2 is a block diagram illustrating a circuit configuration of theradio-frequency module according to the first embodiment;

FIG. 3A is an equivalent circuit diagram of one cell constituting apower-stage amplifier circuit (FIG. 2) formed at a second member of theradio frequency module according to the first embodiment;

FIG. 3B is a sectional view of one cell constituting the power-stageamplifier circuit formed at the second member;

FIGS. 4A to 4F are sectional views of a semiconductor device during amanufacturing process;

FIGS. 5A to 5C are sectional views of the semiconductor device duringthe manufacturing process;

FIG. 5D is a sectional view of the finished semiconductor device;

FIG. 6A illustrates an arrangement of constituent elements of aradio-frequency module according to a second embodiment in plan view;

FIG. 6B schematically illustrates a sectional structure of theradio-frequency module;

FIG. 7A is an equivalent circuit diagram illustrating an example of anoutput matching circuit of the radio-frequency module according to thesecond embodiment;

FIG. 7B illustrates an example of a planar arrangement of constituentelements of the output matching circuit;

FIG. 8A is an equivalent circuit diagram illustrating an example of anoutput matching circuit of a radio-frequency module according to a thirdembodiment;

FIG. 8B illustrates an example of a planar arrangement of constituentelements of the output matching circuit;

FIGS. 9A and 9B schematically illustrate a sectional structure of aradio-frequency module according to a fourth embodiment and a sectionalstructure of a radio-frequency module according to a modification of thefourth embodiment; and

FIG. 10 schematically illustrates a sectional structure of aradio-frequency module according to a fifth embodiment.

DETAILED DESCRIPTION First Embodiment

A radio-frequency module according to a first embodiment will bedescribed with reference to drawings in FIGS. 1A to 5D.

FIG. 1A illustrates an arrangement of constituent elements of aradio-frequency module 20 according to the first embodiment in planview. FIG. 1B schematically illustrates a sectional structure of theradio-frequency module 20. On a module substrate 21, a semiconductordevice 30, an output matching circuit 60, a plurality of duplexers 70, alow-noise amplifier 71, an antenna switch 72, and other surface-mountpassive elements (surface-mount devices (SMDs)) are mounted. Thesemiconductor device 30 includes a first member 31 and a second member32 joined to the first member 31 in surface contact with the firstmember 31. The first member 31 may be made of, for example, an elementalsemiconductor. The second member 32 may be made of, for example, acompound semiconductor.

A band selection switch 41, a first control circuit 42, and an inputswitch 43 are provided at the first member 31. The first member 31includes a semiconductor substrate made of an elemental semiconductorsuch as a silicon substrate or silicon on insulator (SOI) substrate. Theband selection switch 41, the first control circuit 42, and the inputswitch 43 are implemented by, for example, semiconductor elements madeof an elemental semiconductor at a surface layer portion of thesemiconductor substrate.

A radio-frequency amplifier circuit 50 is provided at the second member32. The second member 32 includes, for example, an underlyingsemiconductor layer made of a compound semiconductor such as GaAs and asemiconductor element disposed on or in the underlying semiconductorlayer. The semiconductor element is made from a compound semiconductorand may be, for example, a heterojunction bipolar transistor (HBT). Theradio-frequency amplifier circuit 50 is implemented by, for example, asemiconductor element made of a compound semiconductor.

The output matching circuit 60 is implemented by an integrated passivedevice (IPD) having passive elements including, for example, an inductorand a capacitor. The output matching circuit 60 may be implemented bycombining a plurality of surface-mount passive elements.

The second member 32 is included in the first member 31 in plan view.The semiconductor device 30 has a plurality of conductive protrusions 35arranged at positions within the first member 31 or the second member 32in plan view. The plurality of conductive protrusions 35 are raised fromthe first member 31 or the second member 32 to the module substrate. Thesemiconductor device 30 is flip-chip mounted on or in the modulesubstrate 21 with the plurality of conductive protrusions 35therebetween in such a manner that the second member 32 faces the modulesubstrate 21. Cu pillar bumps formed by depositing solder on the topsurfaces of raised portions made of Cu are used as the plurality ofconductive protrusions 35. Structures without depositing solder on thetop surface such as Au bumps may be used as the conductive protrusions35. Raised portions structured in such manners are also referred to as“pillar”. Alternatively, structures formed by standing conductivecolumns on pads may be used as the conductive protrusions 35. Conductiveprotrusions structured in such a manner are also referred to as “post”.Ball bumps formed in a ball shape by reflow soldering may be used as theconductive protrusions 35. In addition to these various structures,various other structures including conductors raised from a substratemay be used as the conductive protrusions 35.

The low-noise amplifier 71 is flip-chip mounted on or in the modulesubstrate 21 with a plurality of conductive protrusions interposedtherebetween. The output matching circuit 60 and the plurality ofduplexers 70 are flip-chip mounted on or in the module substrate 21 withsolder bumps 65 interposed therebetween. These bumps for flip-chipmounting are an example, and bumps structured in other manners may alsobe used. For example, Au bumps may be used. The electronic componentsmounted on or in the module substrate 21 are sealed by a molding resin25.

An output port of the radio-frequency amplifier circuit 50 provided atthe second member 32 of the semiconductor device 30 is coupled to theoutput matching circuit 60 via the conductive protrusion 35, a wire 22in the module substrate 21, and the solder bump 65 of the outputmatching circuit 60. The output matching circuit 60 is further coupledto the band selection switch 41 provided at the first member 31 viaanother solder bumps 65, another wire 22 in the module substrate 21, andthe conductive protrusion 35 raised from the first member 31. The wires22 are constituted by metal patterns included in a plurality of wiringlayers arranged in the module substrate 21 and a plurality of viasconnecting the wiring layers.

The semiconductor device 30 is disposed in close proximity to the outputmatching circuit 60 in plan view. Here, the expression “thesemiconductor device 30 is disposed in close proximity to the outputmatching circuit 60” denotes that the shortest distance from thesemiconductor device 30 to the output matching circuit 60 is shorterthan the shortest distance from the semiconductor device 30 to anothercircuit component such as the duplexer 70. When the shortest distancefrom the semiconductor device 30 to the output matching circuit 60 isshorter than the shortest distance from the semiconductor device 30 tothe duplexer 70, high isolation can be achieved for transmission andreception.

It is preferable that the semiconductor device 30 and the outputmatching circuit 60 be directly next to each other in plan view. It ispreferable that no circuit component is disposed in an area 24 betweenthe semiconductor device 30 and the output matching circuit 60.

When the output matching circuit 60 is implemented by a plurality ofsurface-mount passive elements, no circuit component is disposed in thearea between the semiconductor device 30 and a closest passive elementof the plurality of surface-mount passive elements constituting theoutput matching circuit 60 to the semiconductor device 30. When theoutput matching circuit 60 includes a plurality of surface-mount passiveelements, the output matching circuit 60 is formed by these passiveelements and wires connecting these passive elements to each other. Itshould be noted that the output matching circuit 60 do not include wiresconnecting these passive elements and circuit components other than theoutput matching circuit 60.

When the output matching circuit 60 is implemented by a single IPD, nocircuit component is disposed between one passive element forming theoutput matching circuit 60, that is, the IPD and the semiconductordevice 30. In this case, when a plurality of passive elements including,for example, a capacitor and an inductor included in the single IPDforming the output matching circuit 60 are brought into focus, nocircuit component is disposed in the area between the semiconductordevice 30 and a closest passive element of the plurality of passiveelements included in the output matching circuit 60 to the semiconductordevice 30.

FIG. 2 is a block diagram illustrating a circuit configuration of theradio-frequency module 20 according to the first embodiment. Theradio-frequency module 20 includes the semiconductor device 30 mountedon or in the module substrate 21. The semiconductor device 30 includesthe input switch 43, the first control circuit 42, and the bandselection switch 41 for transmitting signals that are all provided atthe first member 31. The second member 32 includes the radio-frequencyamplifier circuit 50. The radio-frequency amplifier circuit 50 isconstituted by two stages of a driver-stage amplifier circuit 51 and apower-stage amplifier circuit 52.

Additionally, the output matching circuit 60, the plurality of duplexers70, the antenna switch 72, two band selection switches 73 for receivedsignals, two low-noise amplifiers 71, an output-terminal selectionswitch 74 for received signals, and a second control circuit 75 aredisposed at the module substrate 21. The radio-frequency module 20transmits and receives signals in accordance with a frequency divisionduplex (FDD) system. FIG. 1A does not illustrate the band selectionswitches 73 for received signals, the output-terminal selection switch74, and the second control circuit 75. In FIG. 2, the electroniccircuits provided at the first member 31 are shaded with hatching in arelatively light color, and the electronic circuit provided at thesecond member 32 is shaded with hatching in a relatively dark color.

Two input-side contacts of the input switch 43 are respectively coupledto radio-frequency-signal input terminals IN1 and IN2 of the modulesubstrate 21 via the conductive protrusions 35 (FIG. 1B) provided at thefirst member 31. In FIG. 2, connection points with the conductiveprotrusions 35 are indicated by white squares. Radio-frequency signalsare inputted from the two radio-frequency-signal input terminals IN1 andIN2. The input switch 43 selects one contact from the two input-sidecontacts to cause a radio-frequency signal inputted to the selectedcontact to be inputted to the driver-stage amplifier circuit 51. Aninter-member connection wire 36 is used to connect the input switch 43and an input port of the driver-stage amplifier circuit 51. Theinter-member connection wire 36 couple the electronic circuits providedat the first member 31 and the electronic circuit provided at the secondmember 32 without using the module substrate 21. The structure of theinter-member connection wire 36 will be explained in a description of amanufacturing process provided with reference to drawings in FIGS. 4A to5D. In FIG. 2, connections with the inter-member connection wire 36 areindicated by thicker solid lines.

A radio-frequency signal amplified by the driver-stage amplifier circuit51 is inputted to the power-stage amplifier circuit 52. Aradio-frequency signal amplified by the power-stage amplifier circuit 52is inputted via the output matching circuit 60 to an input-side contactof the band selection switch 41. An output port of the power-stageamplifier circuit 52 and the output matching circuit 60 are coupled toeach other with the conductive protrusion 35 (FIG. 1B) provided at thesecond member 32 and the wire 22 (FIG. 1B) in the module substrate 21interposed therebetween. The output matching circuit 60 and theinput-side contact of the band selection switch 41 are coupled to eachother via the wire 22 (FIG. 1B) provided in the module substrate 21 andthe conductive protrusion 35 (FIG. 1B) provided at the first member 31.The band selection switch 41 selects one contact from a plurality ofoutput-side contacts to cause a radio-frequency signal amplified by thepower-stage amplifier circuit 52 to be outputted from the selectedcontact.

Two contacts of the plurality of output-side contacts of the bandselection switch 41 are coupled to auxiliary output terminals PAAUX1 andPAAUX2 via the conductive protrusions 35 (FIG. 1B). The other sixcontacts are coupled to input ports for transmitting signals of theplurality of duplexers 70 prepared for different bands via theconductive protrusions 35 (FIG. 1B). The band selection switch 41 has afunction of selecting one duplexer 70 from the plurality of duplexers 70prepared for different bands.

The antenna switch 72 includes a plurality of circuit-side contacts andtwo antenna-side contacts. Two contacts of the plurality of circuit-sidecontacts of the antenna switch 72 are individually coupled totransmit-signal input terminals TRX1 and TRX2. The other sixcircuit-side contacts are respectively coupled to input-output commonports of the duplexers 70. The antenna-side two contacts areindividually coupled to antenna terminals ANT1 and ANT2. An antenna iscoupled to each of the antenna terminals ANT1 and ANT2.

The antenna switch 72 connects the two antenna-side contactsindividually to two contacts selected from the plurality of circuit-sidecontacts. When a single band is used for communication, the antennaswitch 72 connects one circuit-side contact to one antenna-side contact.A radio-frequency signal amplified by the radio-frequency amplifiercircuit 50 and transferred through one duplexer 70 of a correspondingband is transmitted from an antenna coupled to the selected antenna-sidecontact.

The two band selection switches 73 for received signals each includefour input-side contacts. Three contacts of the four input-side contactsof each of the two band selection switches 73 are individually coupledto output ports for received signals of the duplexers 70. The other onecontact of each of the two band selection switches 73 is coupled to anauxiliary input terminal LNAAUX1 or LNAAUX2.

The two low-noise amplifiers 71 are prepared for the two band selectionswitches 73 for received signals. The two band selection switches 73 forreceived signals each cause a receive signal having passed through theduplexer 70 to be inputted to the corresponding low-noise amplifier 71.

Two circuit-side contacts of the output-terminal selection switch 74 areindividually coupled to output ports of the two low-noise amplifiers 71.Three terminal-side contacts of the output-terminal selection switch 74are individually coupled to receive-signal output terminals LNAOUT1,LNAOUT2, and LNAOUT3. A receive signal amplified by the low-noiseamplifier 71 is outputted from a receive-signal output terminal selectedby the output-terminal selection switch 74.

Supply voltage is applied to the driver-stage amplifier circuit 51 andthe power-stage amplifier circuit 52 from power supply terminals VCC1and VCC2 provided at the module substrate 21. The power supply terminalsVCC1 and VCC2 are coupled to the radio-frequency amplifier circuit 50via the conductive protrusions 35 (FIG. 1B) provided at the secondmember 32.

The first control circuit 42 are coupled to a power supply terminalVIO1, a control-signal terminal SDATA1, and a clock terminal SCLK1 viathe conductive protrusions 35 (FIG. 1B) provided at the first member 31.The first control circuit 42 controls the radio-frequency amplifiercircuit 50 in accordance with a control signal supplied to thecontrol-signal terminal SDATA1. The inter-member connection wire 36connects the first control circuit 42 and the radio-frequency amplifiercircuit 50 to each other.

The second control circuit 75 is coupled to a power supply terminalVIO2, a control-signal terminal SDATA2, and a clock terminal SCLK2. Thesecond control circuit 75 controls the low-noise amplifier 71, the bandselection switches 73, and the output-terminal selection switch 74 inaccordance with a control signal supplied to the control-signal terminalSDATA2.

A power supply terminal VBAT and a drain-voltage terminal VDD2 areprovided at the module substrate 21. Power is supplied to a bias circuitof the radio-frequency amplifier circuit 50 and the first controlcircuit 42 from the power supply terminal VBAT. Supply voltage isapplied to the low-noise amplifier 71 installed at the module substrate21 from the drain-voltage terminal VDD2.

FIG. 3A is an equivalent circuit diagram of one cell constituting thepower-stage amplifier circuit 52 (FIG. 2) formed at the second member32. The power-stage amplifier circuit 52 includes a plurality of cellsin parallel with each other. Each cell includes a transistor 402, aninput capacitor Cin, and a ballast resistor element Rb. The base of thetransistor 402 is coupled to a radio-frequency-signal input wire 405RFvia the input capacitor Cin. The base of the transistor 402 is coupledto a base bias wire 404BB via the ballast resistor element Rb. Theemitter of the transistor 402 is grounded. Supply voltage is applied tothe collector of the transistor 402, and an amplified radio-frequencysignal is outputted from the collector.

FIG. 3B is a sectional view of one cell constituting the power-stageamplifier circuit 52 formed at the second member 32. The first member 31includes the semiconductor substrate such as a silicon substrate or SOIsubstrate, and a multilayer wiring structure formed on the semiconductorsubstrate. The band selection switch 41, the first control circuit 42,and the input switch 43 (FIG. 1A), which are not illustrated in FIG. 3B,are formed at the surface layer portion of the semiconductor substrateconstituting the first member 31.

The second member 32 includes an underlying semiconductor layer 401. Inthe state in which the underlying semiconductor layer 401 is in surfacecontact with the first member 31, the second member 32 is joined to thefirst member 31. The underlying semiconductor layer 401 is divided intoa conductive area 401A and an element isolation area 401B. Theunderlying semiconductor layer 401 may be made by using, for example,GaAs. The conductive area 401A is made of N-type GaAs. The elementisolation area 401B is made by doping an impurity for non-conductivityto an N-type GaAs layer by ion implantation.

The transistor 402 is disposed on the conductive area 401A. Thetransistor 402 includes a collector layer 402C, a base layer 402B, andan emitter layer 402E, which are stacked on the conductive area 401A inorder. The emitter layer 402E is disposed on a portion of the base layer402B. For example, the collector layer 402C may be made of N-type GaAs,the base layer 402B may be made of P-type GaAs, and the emitter layer402E may be made of N-type InGaP. This means that the transistor 402 isan HBT.

A base electrode 403B is disposed on the base layer 402B. The baseelectrode 403B is electrically coupled to the base layer 402B. Anemitter electrode 403E is disposed on the emitter layer 402E. Theemitter electrode 403E is electrically coupled to the emitter layer402E. A collector electrode 403C is disposed on the conductive area401A. The collector electrode 403C is electrically coupled to thecollector layer 402C via the conductive area 401A.

A first-layer interlayer insulating film 406 is disposed on theunderlying semiconductor layer 401 to cover the transistor 402, thecollector electrode 403C, the base electrode 403B, and the emitterelectrode 403E. The first-layer interlayer insulating film 406 may bemade of, for example, an inorganic insulating material such as SiN. Aplurality of openings are provided at the interlayer insulating film406.

A first-layer emitter wire 404E, a base wire 404B, a collector wire404C, the base bias wire 404BB, and the ballast resistor element Rb aredisposed on the interlayer insulating film 406. The emitter wire 404E iscoupled to the emitter electrode 403E through an opening provided at theinterlayer insulating film 406. The base wire 404B is coupled to thebase electrode 403B through another opening provided at the interlayerinsulating film 406. The collector wire 404C is coupled to the collectorelectrode 403C through another opening provided at the interlayerinsulating film 406.

The base wire 404B extends to an area not including the transistor 402.An end portion of the base wire 404B overlaps the ballast resistorelement Rb in the area. The base wire 404B and the ballast resistorelement Rb are electrically coupled to each other at the overlap. Theother end portion of the ballast resistor element Rb overlaps the basebias wire 404BB. The ballast resistor element Rb and the base bias wire404BB are electrically coupled to each other at the overlap.

A second-layer interlayer insulating film 407 is disposed over theinterlayer insulating film 406 to cover the first-layer emitter wire404E, the base wire 404B, the ballast resistor element Rb, and the basebias wire 404BB. The second-layer interlayer insulating film 407 mayalso be made of, for example, an inorganic insulating material such asSiN.

A second-layer emitter wire 405E and the radio-frequency-signal inputwire 405RF are disposed on the interlayer insulating film 407. Thesecond-layer emitter wire 405E is coupled to the first-layer emitterwire 404E through an opening provided at the interlayer insulating film407. A portion of the radio-frequency-signal input wire 405RF overlapsthe first-layer base wire 404B in plan view. The input capacitor Cin isformed at the area of the overlap of the radio-frequency-signal inputwire 405RF and the first-layer base wire 404B.

A third-layer interlayer insulating film 408 is disposed to cover thesecond-layer emitter wire 405E and the radio-frequency-signal input wire405RF. The third-layer interlayer insulating film 408 may be made of,for example, an organic insulating material such as polyimide.

Next, a method of manufacturing the semiconductor device 30 according tothe first embodiment will be described with reference to drawings inFIGS. 4A to 5D. The drawings in FIGS. 4A to 5C are sectional views ofthe semiconductor device 30 during a manufacturing process. FIG. 5D is asectional view of the finished semiconductor device 30.

As illustrated in FIG. 4A, a release layer 201 is epitaxially grown on asingle-crystal base substrate 200 made from a compound semiconductorsuch as GaAs, and an element formation layer 202 is formed on therelease layer 201. Elements including the electronic circuits of theradio-frequency amplifier circuit 50 formed at the second member 32illustrated in FIG. 2 are formed at the element formation layer 202.These electronic circuits are formed in accordance with a generalsemiconductor manufacturing process. FIG. 4A does not illustrate theelement structures formed at the element formation layer 202. In thisstage, the element formation layer 202 is not divided into theindividual second members 32.

Next, as illustrated in FIG. 4B, the element formation layer 202 (FIG.4A) and the release layer 201 are subjected to patterning by using aresist pattern (not illustrated in the drawing) as an etch mask. In thisstage, the element formation layer 202 (FIG. 4A) is divided into theindividual second members 32.

Next, as illustrated in FIG. 4C, a connecting support 204 is bonded onthe divided second members 32. As a result, the plurality of secondmembers 32 are connected to each other by the connecting support 204.The resist pattern used as an etch mask in the patterning step of FIG.4B may be left so that the resist pattern exists between the secondmember 32 and the connecting support 204.

Next, as illustrated in FIG. 4D, the release layer 201 corresponding tothe base substrate 200 and the second member 32 is selectively etched.As a result, the second member 32 and the connecting support 204 arereleased from the base substrate 200. To selectively etch the releaselayer 201, the release layer 201 is formed from a compound semiconductorhaving an etch resistance different from both the etch resistance of thebase substrate 200 and the etch resistance of the second member 32.

As illustrated in FIG. 4E, a substrate 210 including, for example, theband selection switch 41, the first control circuit 42, and the inputswitch 43 (FIG. 1A) provided at the first member 31 is prepared. In thisstage, the substrate 210 is not divided into the individual firstmembers 31.

As illustrated in FIG. 4F, the second members 32 are joined to thesubstrate 210. The second member 32 and the substrate 210 are joined toeach other by the Van der Waals force or hydrogen bonding. The secondmember 32 may be joined to the substrate 210 by, for example, staticelectricity, covalent bonding, or eutectic alloy bonding. For example,when a portion of a surface of the substrate 210 is made of Au, pressuremay be applied in the state in which the second member 32 is in closecontact with the Au area so as to join the second member 32 and thesubstrate 210.

Next, as illustrated in FIG. 5A, the connecting support 204 is releasedfrom the second member 32. After the connecting support 204 is released,as illustrated in FIG. 5B, an interlayer insulating film 80 and aredistribution layer are formed over the substrate 210 and the secondmember 32. The redistribution layer includes the inter-member connectionwire 36 and a pad 37.

Next, as illustrated in FIG. 5C, a protection film 81 is formed on theredistribution layer, and, for example, openings 81A are formed at theprotection film 81. After this, the conductive protrusions 35 are formedin the openings 81A and on the protection film 81. The reflow process isperformed in the state in which solder joints 83 are laid on topsurfaces of the conductive protrusions 35.

Finally, as illustrated in FIG. 5D, the substrate 210 is cut with adicing machine. As a result, individual pieces of the semiconductordevices 30 can be obtained. The first member 31 of each of theindividual semiconductor devices 30 are larger than the second member 32in plan view. The individual semiconductor device 30 is flip-chipmounted on or in the module substrate 21 (FIGS. 1A and 1B).

Next, advantageous effects of the first embodiment will be described. Inthe first embodiment, the single semiconductor device 30 is formed bystacking the first member 31 including the semiconductor elements madeof an elemental semiconductor and the second member 32 including thesemiconductor element made of a compound semiconductor. As a result, theradio-frequency module 20 can be smaller than if the two members areseparately mounted on or in the module substrate 21. Further, becausethe band selection switch 41 is provided at the first member 31, theradio-frequency module 20 can be smaller than if the band selectionswitch 41 is individually mounted on or in the module substrate 21.

Moreover, two heat transfer paths are formed; one is a heat transferpath along which heat generated at the transistor 402 (FIG. 3B) includedin the second member 32 is transferred to the first member 31 (FIGS. 1Band 5D); and the other is a heat transfer path along which the heat istransferred through the conductive protrusion 35 (FIG. 5D) to the modulesubstrate 21 (FIG. 1B). The first member 31, which is larger than thesecond member 32, and the module substrate 21 function as a heat sink,and as a result, it is possible to improve the characteristic of heatreleased from the transistor 402.

Further, in the first embodiment, the semiconductor device 30 isdisposed in close proximity to the output matching circuit 60. Forexample, no circuit component is disposed in the area 24 (FIG. 1A)between the semiconductor device 30 and the output matching circuit 60in plan view. This can shorten the transfer line from theradio-frequency amplifier circuit 50 to the output matching circuit 60and the transfer line from the output matching circuit 60 to the bandselection switch 41, which are illustrated in FIG. 2. Shortening thetransfer lines can reduce the transfer loss of radio-frequency signal.As a result, it is possible to achieve highly efficient performance.

To shorten the transfer line from the radio-frequency amplifier circuit50 to the output matching circuit 60 and the transfer line from theoutput matching circuit 60 to the band selection switch 41, it ispreferable that the second member 32 and the band selection switch 41 beoffset from the geometrical center of the first member 31 toward theoutput matching circuit 60 in plan view.

Second Embodiment

Next, a radio-frequency module according to a second embodiment will bedescribed with reference to FIGS. 6A to 7B. The following descriptiondoes not repeat configurations common to the radio-frequency moduleaccording to the first embodiment described with reference to FIGS. 1Ato 5D.

FIG. 6A illustrates an arrangement of constituent elements of theradio-frequency module 20 according to the second embodiment in planview. FIG. 6B schematically illustrates a sectional structure of theradio-frequency module 20. In the first embodiment (FIG. 1A), thesemiconductor device 30 does not overlap the output matching circuit 60in plan view, but the semiconductor device 30 is disposed in closeproximity to the output matching circuit 60. By contrast, in the secondembodiment, the semiconductor device 30 overlaps at least a portion ofone or some passive elements of the plurality of passive elementsincluded in the output matching circuit 60 in plan view.

As illustrated in FIG. 6B, the output matching circuit 60 includes aninductor 61 and a capacitor 62. The inductor 61 is formed by a metalpattern disposed on or in the module substrate 21. An individual surfacemount device mounted on or in the module substrate 21 is used as thecapacitor 62. In plan view, the inductor 61 at least partially overlapsthe semiconductor device 30, and the capacitor 62 is disposed in closeproximity to the semiconductor device 30. The capacitor 62 and thesemiconductor device 30 are next to each other in plan view. Forexample, no circuit component is disposed between the semiconductordevice 30 and a closest surface-mount passive element of thesurface-mount passive elements included in the output matching circuit60 to the semiconductor device 30.

FIG. 7A is an equivalent circuit diagram illustrating an example of theoutput matching circuit 60. Series-connected inductors L1 and L2 and aseries-connected capacitor C3 are coupled in series with each otherbetween an output port of the radio-frequency amplifier circuit 50 andthe band selection switch 41. A ground-connected capacitor C1 is coupledbetween the series-connected inductors L1 and L2. A ground-connectedcapacitor C2 is coupled between the series-connected inductor L2 and theseries-connected capacitor C3. A supply voltage Vcc is applied to theoutput port of the radio-frequency amplifier circuit 50 through a chokecoil LC. A decoupling capacitor CD is coupled between the supply voltageVcc and the ground.

FIG. 7B illustrates an example of a planar arrangement of theconstituent elements of the output matching circuit 60. In FIG. 7B,metal patterns in a first wiring layer of the module substrate 21 (FIG.6B) are shaded with hatching in dark diagonal lines from upper right tolower left, and metal patterns in a second wiring layer deeper than thefirst wiring layer are shaded with hatching in light diagonal lines fromupper left to lower right. In the circular area at which a metal patternin the first wiring layer overlaps a metal pattern in the second wiringlayer, a via connecting the metal patterns is positioned. The outputmatching circuit 60 includes passive elements formed by metal patternsdisposed on or in the module substrate 21 and surface-mount passiveelements (SMDs) mounted on or in the module substrate 21.

The series-connected inductor L1 is formed by a spiral metal pattern inthe first wiring layer. The semiconductor device 30 includes theseries-connected inductor L1 in plan view. The metal pattern forming theseries-connected inductor L1 may be shaped as a meander. The otherseries-connected inductor L2 is formed by a metal pattern in the firstwiring layer disposed outside the semiconductor device 30 in plan view.

Individual surface-mount passive elements (SMDs) are used as theground-connected capacitors C1 and C2 and the series-connected capacitorC3. No circuit component is disposed between the semiconductor device 30and a closest passive element of the plurality of individualsurface-mount passive elements constituting the output matching circuit60, namely, the ground-connected capacitors C1 and C2 and theseries-connected capacitor C3 to the semiconductor device 30. No circuitcomponent is disposed between the semiconductor device 30 and a closestpassive element of the passive elements disposed outside thesemiconductor device 30 in plan view out of the plurality of passiveelements constituting the output matching circuit 60, namely, theground-connected capacitors C1 and C2, the series-connected capacitorC3, and the series-connected inductor L2 to the semiconductor device 30.The area between the series-connected inductor L2 and the semiconductordevice 30 does not include any circuit component not constituting theoutput matching circuit 60.

Next, advantageous effects of the second embodiment will be described.Because in the second embodiment a portion of the output matchingcircuit 60 overlaps the semiconductor device 30 in plan view, theradio-frequency module can be further miniaturized. Furthermore,similarly to the first embodiment, it is possible to achieve the effectof improving the characteristic of heat release and the effect ofreducing transfer loss.

Next, modifications of the second embodiment will be described. Theseries-connected inductor L2 is implemented by a metal pattern providedat the module substrate 21 in the second embodiment, but theseries-connected inductor L2 may be implemented by an individual surfacemount device. Surface mount devices are used for all theground-connected capacitors C1 and C2 and the series-connected capacitorC3 in the second embodiment, but the capacitors may be partiallyimplemented by the built-in capacitance of the band selection switch 41.Another example of configuration is that digitally tunable capacitorsmay be used as the ground-connected capacitors C1 and C2 and theseries-connected capacitor C3.

It is preferable that a passive element for high Q factor be implementedby a metal pattern in the module substrate 21 or a surface mount device.A passive element without need for high Q factor may be provided at thefirst member 31. For example, the series-connected capacitor C3 is notrequired to achieve high Q factor as compared to the other passiveelements. Thus, the series-connected capacitor C3 can be formed at thefirst member 31.

Third Embodiment

Next, a radio-frequency module according to a third embodiment will bedescribed with reference to FIGS. 8A and 8B. The following descriptiondoes not repeat configurations common to the radio-frequency moduleaccording to the second embodiment described with reference to FIGS. 6Ato 7B.

FIG. 8A is an equivalent circuit diagram illustrating an example of theoutput matching circuit 60. A single-ended amplifier circuit is used asthe radio-frequency amplifier circuit 50 in the second embodiment, but adifferential amplifier circuit is used as the radio-frequency amplifiercircuit 50 in the third embodiment. The radio-frequency amplifiercircuit 50 has two output ports for outputting differential signals. Theoutput matching circuit 60 includes an output transformer having aprimary coil L5 and a secondary coil L6, a ground-connected capacitorC5, and a series-connected capacitor C6.

The primary coil L5 of the output transformer is coupled between the twooutput ports. A center tap of the primary coil L5 is coupled to thesupply voltage Vcc. One end portion of the secondary coil L6 of theoutput transformer is coupled to the band selection switch 41 via theseries-connected capacitor C6. The one end portion of the secondary coilL6 is also grounded via the ground-connected capacitor C5. The other endportion of the secondary coil L6 is grounded.

FIG. 8B illustrates an example of a planar arrangement of theconstituent elements of the output matching circuit 60. In FIG. 8B,metal patterns in the first wiring layer of the module substrate 21(FIG. 6B) are shaded with hatching in dark diagonal lines from upperright to lower left, and a metal pattern in the second wiring layer isshaded with hatching in light diagonal lines from upper left to lowerright. The metal pattern in the second wiring layer forms the primarycoil L5. The secondary coil L6 formed by a metal pattern in the firstwiring layer is disposed around the primary coil L5. Instead of thestructure in which the secondary coil L6 is disposed around the primarycoil L5, the primary coil L5 may substantially overlap the secondarycoil L6 in plan view. Individual surface mount devices are used as theground-connected capacitor C5 and the series-connected capacitor C6.Both the primary coil L5 and the secondary coil L6 partially overlap thesemiconductor device 30 in plan view.

Next, advantageous effects of the third embodiment will be described.Similarly to the second embodiment, because in the third embodiment aportion of the output matching circuit 60 also overlaps thesemiconductor device 30 in plan view, the radio-frequency module can befurther miniaturized. Furthermore, similarly to the second embodiment,it is possible to achieve the effect of improving the characteristic ofheat release and the effect of reducing transfer loss.

Fourth Embodiment

Next, a radio-frequency module according to a fourth embodiment will bedescribed with reference to FIG. 9A. The following description does notrepeat configurations common to the radio-frequency module according tothe first embodiment described with reference to FIGS. 1A to 5D.

FIG. 9A schematically illustrates a sectional structure of theradio-frequency module 20 according to the fourth embodiment. A printedcircuit board with elements on one side is used as the module substrate21 in the first embodiment, but a printed circuit board with elements onboth sides is used as the module substrate 21 in the fourth embodiment.

The semiconductor device 30 and the plurality of duplexers 70 aremounted on a first surface 21A that is one surface of the modulesubstrate 21. The output matching circuit 60, the low-noise amplifier71, and the antenna switch 72 are mounted on a second surface 21Bopposite to the first surface 21A. An integrated passive device is usedas the output matching circuit 60. The output matching circuit 60 may beimplemented by a plurality of surface mount devices. The output matchingcircuit 60 overlaps the semiconductor device 30 in plan view. When theoutput matching circuit 60 is implemented by a plurality of surfacemount devices, at least one or some surface mount devices of theplurality of surface mount devices overlap the semiconductor device 30in plan view.

The radio-frequency amplifier circuit 50 formed at the second member 32is coupled to the output matching circuit 60 via the conductiveprotrusion 35 raised from the second member 32, the wire 22 extendingfrom the first surface 21A to the second surface 21B in the modulesubstrate 21, and the solder bump 65 of the output matching circuit 60.The output matching circuit 60 is further coupled to the band selectionswitch 41 via another solder bump 65, another wire 22, and theconductive protrusion 35 raised from the first member 31. The solderbumps 65 can be replaced with conductive protrusions having another kindof structure such as Cu pillar bumps, pillars, or posts.

A plurality of conductive columns 27 are attached to the second surface21B of the module substrate 21 in such a manner that the plurality ofconductive columns 27 are almost perpendicular to the second surface21B. The elements mounted on the first surface 21A of the modulesubstrate 21 such as the semiconductor device 30 and the duplexers 70are sealed by the molding resin 25. The elements mounted on the secondsurface 21B such as the output matching circuit 60, the low-noiseamplifier 71, and the antenna switch 72 are sealed by a molding resin26. An end of each of the plurality of conductive columns 27 is exposedfrom the surface of the molding resin 26. The surface of the exposed endof each of the plurality of conductive columns 27 is used as anelectrode terminal for establishing connection with, for example, amotherboard. A ball bump (also referred to as solder bump) made ofsolder may be deposited on the surface of the exposed end of each of theplurality of conductive columns 27. For example, a Cu pillar bump or apillar may be disposed on the exposed surface of each of the pluralityof conductive columns 27. Another example is that, for example, Cupillar bumps, pillars, or solder bumps may be used as a replacement forthe conductive columns 27.

Next, advantageous effects of the fourth embodiment will be described.In the fourth embodiment, the semiconductor device 30 and the outputmatching circuit 60 are respectively disposed on different sides acrossthe module substrate 21, and the semiconductor device 30 and the outputmatching circuit 60 overlap in plan view. This structure can furthershorten the wire 22 connecting the radio-frequency amplifier circuit 50of the semiconductor device 30 and the output matching circuit 60 andthe wire 22 connecting the output matching circuit 60 and the bandselection switch 41. In FIG. 9A, a curved line with an arrow indicatesthe transfer path of radio-frequency signal from the radio-frequencyamplifier circuit 50 via the output matching circuit 60 to the bandselection switch 41. Because the transfer path is relatively short, itis possible to reduce the transfer loss of radio-frequency signal andachieve highly efficient performance. Furthermore, also in the fourthembodiment, it is possible to improve the characteristic of heat releaseand achieve miniaturization, similarly to the first embodiment.

Next, the radio-frequency module 20 according to a modification of thefourth embodiment will be described with reference to FIG. 9B.

FIG. 9B schematically illustrates a sectional structure of theradio-frequency module 20 according to a modification of the fourthembodiment. In the fourth embodiment (FIG. 9A), the semiconductor device30 is mounted on the first surface 21A of the module substrate 21, andthe output matching circuit 60 is mounted on the second surface 21B,that is, a surface facing the motherboard when the radio-frequencymodule 20 is mounted on or in the motherboard. By contrast, in thismodification, the semiconductor device 30 is mounted on the secondsurface 21B of the module substrate 21, that is, the surface facing themotherboard when the radio-frequency module 20 is mounted on or in themotherboard. The output matching circuit 60 is mounted on the firstsurface 21A opposite to the second surface 21B having the semiconductordevice 30. Also in this modification, the output matching circuit 60overlaps the semiconductor device 30 in plan view. Also in FIG. 9B,similarly to FIG. 9A, a curved line with an arrow indicates the transferpath of radio-frequency signal.

As illustrated in the fourth embodiment and its modification, either thesemiconductor device 30 or the output matching circuit 60 can be mountedon the surface facing the motherboard. In either case, the outputmatching circuit 60 is mounted on the surface opposite to the surfacehaving the semiconductor device 30.

Fifth Embodiment

Next, a radio-frequency module according to a fifth embodiment will bedescribed with reference to FIG. 10. The following description does notrepeat configurations common to the radio-frequency module 20 (FIG. 9A)according to the fourth embodiment.

FIG. 10 schematically illustrates a sectional structure of theradio-frequency module 20 according to the fifth embodiment. In thefourth embodiment, the output matching circuit 60 is constituted by anintegrated passive device or a plurality of surface mount devices. Bycontrast, in the fifth embodiment, the inductor 61 included in theoutput matching circuit 60 is implemented by a metal pattern included ina wiring layer of the module substrate 21. An individual surface mountdevice is used as the capacitor 62. The surface mount deviceconstituting the output matching circuit 60 is mounted on the surfaceopposite to the surface having the semiconductor device 30.

The inductor 61 at least partially overlaps the semiconductor device 30in plan view. The capacitor 62 also at least partially overlaps thesemiconductor device 30 in plan view.

Next, advantageous effects of the fifth embodiment will be described.Similarly to the fourth embodiment, the fifth embodiment can alsominiaturize the radio-frequency module 20, achieve low loss, and improvethe characteristic of heat release.

The embodiments described above are mere examples, and as might beexpected, the configurations described in the different embodiments maybe partially replaced or combined with each other. In particular, almostidentical effects and advantages achieved by almost identicalconfigurations in the plurality of embodiments are not mentioned inevery embodiment. Moreover, the present disclosure is not limited to theembodiments described above. For example, various modifications,improvements, and combinations would be apparent to those skilled in theart.

What is claimed is:
 1. A radio-frequency module comprising: a modulesubstrate; a semiconductor device mounted on or in the module substrate,the semiconductor device including a radio-frequency amplifier circuitand a band selection switch; and an output matching circuit disposed onor in the module substrate, the output matching circuit being coupledbetween the radio-frequency amplifier circuit and the band selectionswitch, wherein the band selection switch is configured to output aninputted radio-frequency signal from a contact selected from a pluralityof contacts, the semiconductor device includes a first member includingthe band selection switch including a semiconductor element made of anelemental semiconductor, a second member joined to the first member insurface contact with the first member, the second member including theradio-frequency amplifier circuit including a semiconductor element madeof a compound semiconductor, and a plurality of conductive protrusionsarranged at positions included in the first member or the second memberin plan view, the semiconductor device is mounted on or in the modulesubstrate with the plurality of conductive protrusions interposedbetween the semiconductor device and the module substrate such that thesecond member faces the module substrate, and the semiconductor deviceis disposed in a proximity to the output matching circuit in plan view,or the semiconductor device overlaps at least one passive elementconstituting the output matching circuit in plan view.
 2. Theradio-frequency module according to claim 1, wherein the output matchingcircuit includes a passive element configured by a metal patterndisposed on or in the module substrate, and the semiconductor deviceoverlaps at least a portion of the metal pattern configuring the passiveelement of the output matching circuit in plan view.
 3. Theradio-frequency module according to claim 1, wherein the output matchingcircuit includes a passive element mounted on or in the modulesubstrate, and the passive element included in the output matchingcircuit is mounted on a surface of the module substrate, and the surfaceis opposite to another surface having the semiconductor device.
 4. Theradio-frequency module according to claim 3, wherein the semiconductordevice overlaps the passive element included in the output matchingcircuit in plan view.
 5. The radio-frequency module according to claim2, wherein the output matching circuit includes a passive elementmounted on or in the module substrate, and the passive element includedin the output matching circuit is mounted on a surface of the modulesubstrate, and the surface is opposite to another surface having thesemiconductor device.
 6. The radio-frequency module according to claim5, wherein the semiconductor device overlaps the passive elementincluded in the output matching circuit in plan view.